Mechanism of chain initiation by dextransucrase: Absence of terminal ‘sucrose’ linkage in newly synthesized dextran chains

Dextran was synthesized using dextransucrase from Streptococus sanguis 10558 and (F)-[¹⁴C]sucrose as substrate to test the possibility that sucrose may be the initial acceptor for glucose. If sucrose is the initial acceptor, then dextran chains should have [¹⁴C] fructose in a terminal ‘sucrose’ linkage which can be cleaved under mild conditions. Although incorporation of [¹⁴C]fructose into dextran was observed, the label was not released by mild hydrolysis, indicating that sucrose is not the initiator for dextran synthesis. Incorporation of [¹⁴C]fructose into dextran might represent its ability to act as an acceptor, as suggested by the isolation of leucrose as a by-product in the reaction.     

基于多组织稳定同位素比值的热带大西洋4种鲨鱼营养生态位分化

不同代谢速率组织间的碳、氮稳定同位素比值(δ¹³C和δ¹⁵N)可以反映生物不同时间尺度的摄食信息,对探讨物种间摄食、栖息地利用和营养生态位的变化具有重要的指示作用。本研究以在大西洋热带海域兼捕的大青鲨、长鳍鲭鲨、拟锥齿鲨和尖吻鲭鲨为对象,通过测定其肌肉、肝脏和血液的δ¹³C和δ¹⁵N值,探讨4种鲨鱼营养生态位分化。结果表明: 与长鳍鲭鲨相比,尖吻鲭鲨、拟锥齿鲨和大青鲨的δ¹⁵N值相似且相对较高;大青鲨与其他鲨鱼存在摄食隔离,表现出独特的营养生态位;尖吻鲭鲨营养生态位宽幅最大,摄食食物种类和(或)栖息环境类型更多样化,其与拟锥齿鲨的营养生态位重叠度最高,说明两种鲨鱼具有潜在的资源竞争关系。尖吻鲭鲨、拟锥齿鲨和大青鲨组织间的δ¹³C、δ¹⁵N差值与其叉长均无显著相关关系,说明3种鲨鱼近期内无明显摄食变化;而长鳍鲭鲨的肝脏、血液和肌肉组织的δ¹⁵N差值与叉长显著相关,说明长鳍鲭鲨在短期内存在摄食变化。肝脏和血液的δ¹³C、δ¹⁵N值的相似性反映了两种组织整合摄食时间周期相近,其较高的代谢速率可以反映相对短时间周期的摄食信息。     

典型滨岸草地生态系统碳稳定同位素组成及分布特征

通过测定上海市青浦区东风港百慕大、白花三叶草、高羊茅和白茅等4种典型滨岸草本植物各组织以及不同垂直深度土壤有机质δ¹³C值,对滨岸草地生态系统的植物-土壤碳稳定同位素特征进行了分析.结果表明: 白花三叶草、高羊茅属于C3植物,百慕大、白茅属于C4植物,其茎叶、凋落物和根系各组织间δ¹³C值无显著差异.C3和C4植物样带表层土壤有机质δ¹³C值随着土壤深度递增而呈现截然不同的变化特征,这与样带本底δ¹³C值以及碳稳定同位素分馏效应有关,同时还受植物根系分布深度的影响.植物输入是土壤有机碳(SOC)的最主要来源,植物有机体δ¹³C组成对土壤有机质δ¹³C值有直接影响,植物各组分δ¹³C值与土壤有机质δ¹³C值均存在极显著相关.4种草本植物样带SOC含量与δ¹³C值均呈极显著相关,其中,C3植物样带SOC含量与δ¹³C值呈线性负相关,C4植物样带SOC含量与δ¹³C值呈线性正相关.     

基于碳、氮稳定同位素研究胶州湾普氏栉虾虎鱼的摄食习性

普氏栉虾虎鱼属于小型暖温性底层鱼类,是胶州湾鱼类群落中的优势种之一,在胶州湾食物网和生态系统中发挥着重要作用.本文应用碳、氮稳定同位素技术,基于胶州湾渔业资源底拖网调查采集的样品,对普氏栉虾虎鱼的摄食习性进行了研究.结果表明: 胶州湾普氏栉虾虎鱼的δ¹⁵N值范围为11.24‰～13.99‰,平均值为(12.70±0.70)‰,δ¹³C值范围为-20.67‰～-18.46‰,平均值为(-19.08±0.36)‰;各体长组的营养级范围为3.49～3.76,平均营养级为(3.62±0.21),其δ¹⁵N值和营养级与体长呈显著负相关,δ¹³C值与体长无显著相关性.普氏栉虾虎鱼摄食的主要饵料生物类群为多毛类、虾类和软体动物,浮游动物和颗粒有机物(POM)的饵料贡献率较小.聚类分析结果表明,普氏栉虾虎鱼各体长组食物组成的相似性均在92%以上,相似性较高,说明其摄食习性随体长变化无明显差异.普氏栉虾虎鱼在胶州湾生态系统中属于中级消费者,其摄食各饵料生物类群比例的变化可能是其营养级与体长呈负相关关系的主要原因.     

Transport in C4 mesophyll chloroplasts. Characterization of the pyruvate carrier

1. Evidence is presented for high rates of carrier-mediated uptake of pyruvate into the stroma of intact mesophyll chloroplasts of the C₄ plant Digitaria sanguinalis, but not the chloroplasts of the C₃ plant Spinacea oleracea. Uptake of pyruvate in the dark with the C₄ mesophyll chloroplasts was followed using two techniques: uptake of [¹⁴C]pyruvate as determined by silicon oil centrifugal filtration and uptake as indicated by absorbance changes at 535 nm (shrinkage/swelling) after addition of 0.1 M pyruvate salts.

2. Uptake of the pyruvate anion by an electrogenic carrier is suggested to be the major mode of transport. Chloroplast swelling was observed in potassium pyruvate plus valinomycin and uptake of [¹⁴C]pyruvate was inhibited by membrane-permeant anions. Valinomycin reduced uptake in the absence of external potassium and the inhibition could be reversed by addition of external potassium.

3. Uptake of pyruvic acid (or a pyruvate ⁻/OH⁻ antiport) is ruled unlikely since [¹⁴C]pyruvate uptake was relatively independent of the pH gradient across the envelope and addition of pyruvate to chloroplasts did not result in an alkalization of the medium. The low rate of swelling observed in ammonium pyruvate may be due to non-mediated permeation of pyruvic acid, which is possible only at high pyruvate concentrations.

4. The concentration of pyruvate in the stroma increased with external concentration over the range tested (up to 40 mM) but the concentration ratio (internal/external) was always less than one. The steady-state concentration of [¹⁴C]pyruvate in the stroma was dependent on the ionic strength of the medium, with saturation at roughly I = 0.04 M, while accumulation of the membrane-permeant cation tetraphenylmethylphosphonium decreased with increasing ionic strength. This suggests that ionic strength modifies a membrane potential (inside negative) across the envelope and that pyruvate uptake responds to the magnitude and direction of that potential (−80 mV at low ionic strength).

5. Chloride and inorganic phosphate were potent inhibitors of [¹⁴C]pyruvate uptake. Of the sulfhydryl reagents tested, N-ethylmaleimide was not inhibitory while mersalyl completely blocked [¹⁴C]pyruvate uptake and swelling in potassium pyruvate plus valinomycin. Pyruvate uptake, as measured by valinomycin induced swelling in potassium pyruvate, was highly temperature sensitive, with an energy of activation of 39 kcal/mol above 9 °C.

6. Phenylpyruvate, -ketoisovalerate, -ketoisocaproate, -cyano-4-hydroxycinnamic acid and -cyanocinnamic acid inhibited [¹⁴C]pyruvate but not [¹⁴C]-acetate uptake in the dark and also reduced pyruvate metabolism by the chloroplasts in the light.     

基于胃含物和稳定同位素研究海州湾长蛇鲻的摄食习性

长蛇鲻(Saurida elongate)为温水性近海底栖鱼类,是目前海州湾的优势鱼种之一,在海州湾食物网中占据重要地位。本研究基于海州湾底拖网调查采集的样品,结合胃含物分析和碳、氮稳定同位素技术,分析了长蛇鲻的摄食习性。结果表明: 海州湾长蛇鲻摄食的主要饵料生物为戴氏赤虾、枪乌贼、长丝虾虎鱼、鳀、六丝钝尾虾虎鱼、细条天竺鲷、尖海龙和绯鱼衔。其δ¹³C值范围在-19.39‰～-16.23‰之间,平均值为(-18.01±0.85)‰,与体长无显著相关性;δ¹⁵N值范围在9.56‰～13.36‰之间,平均值为(11.77±0.86)‰,与体长呈显著正相关。长蛇鲻不同体长组的饵料生物贡献度差异较大,随着体长增加,其捕食能力增强、摄食器官逐渐完善、摄食饵料生物的比例发生变化,可能是导致其摄食习性随体长变化的主要原因。本研究有助于深入了解海州湾长蛇鲻的摄食生态,为海州湾食物网营养动力学研究提供了基础资料。     

鬼箭锦鸡儿叶片和土壤碳稳定同位素特征及其影响因素

为探究高海拔地区的植物碳(C)循环过程与其生境的关系,以生长在高山地区的豆科灌木鬼箭锦鸡儿为研究对象,沿着横跨我国东西部山区的样带采集35个样点的鬼箭锦鸡儿叶片和土壤样品,分析了鬼箭锦鸡儿叶片碳稳定同位素组成(δ¹³C)、土壤δ¹³C、叶片和土壤δ¹³C差值(Δδ¹³C)在不同采样点的特征及其与气候因子、叶片和土壤元素的关系。结果表明:鬼箭锦鸡儿叶片δ¹³C的变化范围为-30.9‰～-27.1‰,平均值为-28.4‰,土壤δ¹³C的变化范围为-26.2‰～-23.2‰,平均值为-25.3‰,Δδ¹³C的变化范围为2.0‰～7.7‰,平均值为3.1‰;叶片δ¹³C显著低于土壤δ¹³C,且随着叶片δ¹³C增加,土壤δ¹³C先降低后升高;叶片δ¹³C与生长季均温和叶片C含量呈显著负相关,土壤δ¹³C与相对湿度和最暖月均温呈显著负相关,与土壤碳∶氮(C∶N)呈显著正相关,随土壤C含量的增加土壤δ¹³C先降低后升高,Δδ¹³C与叶片C含量、土壤C含量和土壤C∶N呈显著正相关;气候因子对叶片δ¹³C和Δδ¹³C具有直接影响,同时也通过对叶片和土壤元素的影响,间接导致叶片δ¹³C、土壤δ¹³C和Δδ¹³C的改变。高海拔地区的气候因子、叶片和土壤元素共同影响鬼箭锦鸡儿的C循环过程。     

Main sterols from the ophiuroids Ophiocoma echinata, Ophiocoma wendtii, Ophioplocus januarii and Ophionotus victoriae

Sterol compositions of the cold water ophiuroids Ophioplocus januarii and Ophionotus victoriae and of the tropical ophiuroids Ophiocoma echinata and Ophiocoma wendtii are reported. The four sterol mixtures contain Δ⁵ mono- and di-unsaturated common 3β-hydroxy-sterols. Ophioplocus januarii and O. victoriae contain 24-methylcholesta-5,24(28)-dien-3β-ol and 24ζ-ethylcholesta-5,24(28)-dien-3β-ol in higher abundance than in O. echinata. These sterols were not found in O. wendtii. An interesting finding is the presence of Δ^5,24(28)-24-n-propylidenecholesterol in 7.6% in Ophionotus victoriae.     

On the mechanism of biosynthesis of leukotrienes and related compounds

[10D-³H; 3-¹⁴C]- and [10L-³H; 3-¹⁴C]arachidonic acids were incubated with human polymorphonuclear leukocytes and with human platelets. Leukotriene B₄ and 5(S),12(S)-dihydroxy-6trans,8cis,10trans,14-cis-eicosatetraenoic acid (5,12-DHETE) were isolated and the ³H/¹⁴C ratios determined. It could be concluded that the 10D (pro-R)-hydrogen is eliminated in the conversion of 5(S)-hydroperoxy-6trans,8cis,11cis,14cis-eicosatetraenoic acid into leukotriene A₄ whereas in the conversion of arachidonic acid into 5,12-DHETE the 10L (pro-S)-hydrogen is lost. Incubation of the doubly labeled arachidonic acids with human platelets confirmed and extended previous data on the stereochemistry of the hydrogen removal from C-10 during the conversion into 12(S)-hydroperoxy-5cis,8cis,10trans,14cis-eicosatetraenoic acid, i.e., the 10L (pro-S)-hydrogen is eliminated and the 10D (pro-R)-hydrogen retained.     

栓皮栎叶片δ13C和δ15N的纬向趋势及其影响因子

以东亚广布种栓皮栎为例,通过对南北样带(26°-40° N)上7个群体的调查取样,并结合2个生活史阶段,探讨栓皮栎碳氮同位素比值随纬度环境的变异规律.结果表明: 在纬向梯度上,栓皮栎叶片δ¹³C和δ¹⁵N随纬度的增加分别呈现非线性的增加和下降趋势,且成年树叶片δ¹³C和δ¹⁵N均显著高于幼树;同时,树龄和纬度对叶片δ¹⁵N和δ¹³C均无显著交互作用,表明栓皮栎幼树和成年树纬向环境变化的响应较为一致.随机森林模型结果显示,栓皮栎叶片δ¹⁵N主要受土壤养分,如土壤有机质、磷和氮含量的影响,而叶片δ¹³C主要受水分因子,如空气相对湿度、降水量等的影响.     

Quantitative Measurement of the Diastereoisomers of CIS Thymidine Glycol in Gamma-Irradiated DNA

A technique for determing the relative content of each of the diastereoisomers of cis thymidine glycol (dTG) in DNA exposed to ionizing radiation has been developed. [³H]thymidine DNA was gamma-irradiated, digested to 2'-deoxyribonucleosides, authentic [¹⁴C] (+, -) cis dTG added to the digestate and the mixture resolved by HPLC. ³H fractions coeluting with [¹⁴C] (+, -) dTG were collected and acetylated.

The acetoxy derivatives.of (+) and (-) cis dTG were easily resolved by a second HPLC analysis and their absolute configuration determined by NMR amd mass spectroscopies. We have constructed a dose-response curve for formation of each isomer in gamma-irradiated DNA and shown that they are formed in equal amounts. This technique may be used to determine the relative formation of cis dTG isomers in DNA resulting from other oxidative stresses and whether repair of these is influenced by their configuration.     

栓皮栎叶片δ13C和δ15N的纬向趋势及其影响因子

以东亚广布种栓皮栎为例,通过对南北样带(26°-40° N)上7个群体的调查取样,并结合2个生活史阶段,探讨栓皮栎碳氮同位素比值随纬度环境的变异规律.结果表明: 在纬向梯度上,栓皮栎叶片δ¹³C和δ¹⁵N随纬度的增加分别呈现非线性的增加和下降趋势,且成年树叶片δ¹³C和δ¹⁵N均显著高于幼树;同时,树龄和纬度对叶片δ¹⁵N和δ¹³C均无显著交互作用,表明栓皮栎幼树和成年树纬向环境变化的响应较为一致.随机森林模型结果显示,栓皮栎叶片δ¹⁵N主要受土壤养分,如土壤有机质、磷和氮含量的影响,而叶片δ¹³C主要受水分因子,如空气相对湿度、降水量等的影响.     

基于胃含物和碳、氮稳定同位素研究浙江南部近海蓝圆鲹的摄食生态

蓝圆鲹是浙江南部近海的重要经济鱼类。本文根据2020年5月、8月、11月和2021年1月在浙江南部近海进行的底拖网调查,应用胃含物分析和碳氮稳定同位素分析对浙江南部近海蓝圆鲹的摄食习性进行研究。结果表明: 浙江南部近海蓝圆鲹δ¹³C平均值为(-16.55±0.60)‰,范围为-17.76‰～-15.25‰,与叉长呈显著负相关;蓝圆鲹δ¹⁵N平均值为(11.76±0.88)‰,范围为9.06‰～13.03‰,与叉长呈显著正相关。根据δ¹⁵N值计算浙江南部近海蓝圆鲹的平均营养级为3.89±0.26。胃含物分析表明,浙江南部近海蓝圆鲹的主要饵料类群为鱼类、虾类、蟹类、头足类、多毛类和小型甲壳类。稳定同位素分析表明,虾类对浙江南部近海蓝圆鲹的营养贡献率最高(40%～84%),其次为多毛类、小型甲壳类、蟹类、头足类和鱼类。蓝圆鲹的摄食习性有明显的生长变化,随着蓝圆鲹叉长的增加,其倾向于摄食更高营养级的饵料生物。     

Effects of vesamicol on acetylcholine metabolism and synaptic transmission in the electric organ of Torpedo

Vesamicol [2-(4-phenylpiperidino)cyclohexanol, formerly AH5183] at a concentration of 10 μM reduced by 16–20% the amount of vesicle-bound ACh in intact pieces of Torpedo electric organ (isolated prisms). When [¹⁴C]acetate was applied to prisms in the presence of 10 μM vesamicol, vesicular translocation of newly synthesized [¹⁴C]ACh was inhibited by 40%. During short trains of field shocks given at 10 Hz to the tissue, vesamicol inhibited by 93% the release of [¹⁴C]ACh, but left the release of prestored ACh unaltered. In spite of these alterations, 10 μM vesamicol did not impair nerve-electroplaque transmission, even after prolonged electrical stimulation and during a recovery period. It is concluded that in the Torpedo electric organ the actions of vesamicol on ACh metabolism have apparently little or no effect on the efficiency of synaptic transmission.     

Steroid metabolism in the hormone dependent MCF-7 human breast carcinoma cell line and its two hormone resistant subpopulations MCF-7/LCC1 and MCF-7/LCC2

Androgen and estrogen metabolism was investigated in the hormone-dependent human breast cancer cell line MCF-7 and its two hormone-resistant sublines MCF-7/LCC1 and MCF-7/LCC2. Using the product isolation method, the activity of aromatase, 5-reductase, 3/β-hydroxysteroid oxidoreductase and 17β-hydroxysteroid oxidoreductase were investigated isolating the following steroids: estriol (E₃), estradiol (E₂), estrone (E₁), 3/β-androstanediol (A-diol), testosterone (T), dihydrotestosterone (DHT), androsterone (AND), androstenedion (4-AD) and androstanedione (A-dion). For all experiments, cells were preincubated with cortisol and subsequently incubated with [¹⁴C]T or [¹⁴C]4-AD as the substrate in medium without phenol red and with serum charcoal stripped of steroids. The results showed no aromatase activity in any of the cell lines under the experimental conditions used, and preincubation with cortisol had no effect on the enzyme activity. With [¹⁴C]T as the substrate, the metabolized level of DHT was very similar in the three cell lines, though MCF-7/LCC1 and MCF-7/LCC2 utilized the substrate to a much lesser extent. The amount of DHT and 4-AD produced were comparable in the two hormone-resistant cell lines, while the amount of 4-AD was significantly higher in MCF-7 cells. No differences in enzyme activity were found in the three cell lines when [¹⁴C]4-AD was used as the substrate. This study showed an altered androgen metabolism in the MCF-7/LCC1 and MCF-7/LCC2 sublines compared to the parent MCF-7. However, since treatment with DHT and T inhibited cell growth equally well in all three tumor cell lines, it is unlikely that the found differences in steroid metabolism was involved in the acquisition of the endocrine resistance of the two MCF-7 sublines.     

Purification of pea nodule symbiosomes using an aqueous polymer two-phase system

Symbiosomes were obtained from mature pea (Pisum sativum cv. Argona) root nodules infected with a Rhizobium leguminosarum strain (biov. viciae 3841) and purified using an aqueous polymer two-phase system (APS). The APS consists of a mixture of polymers, usually dextran T500 and poly(ethylene glycol) 3350, prepared as aqueous solutions on a weight per weight basis, where each fraction distributes according to their surface characteristics. Results of ATPase activity, cytochrome c oxidase activity, glucan synthase II activity, NAD(P)H-cytochrome c reductase activity, NO₃⁻-sensitive ATPase activity, transport of [¹⁴C]malate vs. [¹⁴C]glutamate and MAC 57 antigen analysis showed that the APS method provided intact symbiosomes with low bacteroid, plasma membrane, endoplasmic reticulum and/or mitochondria contamination. No complicated equipment is needed and the method was simple and fast, compared with other purification techniques.     

大连海域食物网连续营养谱

根据2008年1月—2017年6月在大连海域收集的因搁浅、误捕及救助无效而死亡的斑海豹、江豚、小须鲸等海洋哺乳动物及2016年秋季和2017年春季在该海域进行的渔业资源调查,应用稳定同位素技术,分析了大连海域海洋哺乳动物及主要生物样品的碳、氮稳定同位素比值(δ¹³C、δ¹⁵N),并计算其营养级,进而构建大连海域食物网的连续营养谱.结果表明: 大连海域食物网的δ¹⁵N值范围为8.0‰～14.7‰,δ¹³C值范围为-21.1‰～-16.7‰.主要生物种类可划分为初级消费者、次级消费者及顶级捕食者3个营养组群.δ¹⁵N值分析显示,主要生物种类的营养级范围为2.63～4.59,其中,小须鲸、江豚、斑海豹的营养级依次为3.16、4.11、4.25,棘皮动物为3.24～3.84,头足类为3.81～3.93,腹足类为3.65～4.13,双壳类为2.63～3.15,甲壳类为3.58～4.12,鱼类为3.20～4.59.营养结构特征显示,初级消费者主要为双壳类,次级消费者主要为小须鲸、头足类、棘皮类、腹足类、甲壳类,顶级捕食者主要为江豚、斑海豹、鱼类.随着江豚体长的增加,δ¹⁵N值有增大趋势,说明随着江豚生长和摄食能力的增强,其摄食的食物趋向于更高营养层次的生物.研究建立了大连海域食物网的连续营养谱,可以为海洋哺乳动物和渔业资源的保护提供依据.     

Phycomyces blakesleeanus car B mutants: Their use in assays of phytoene desaturase

Strains of car B (phytoene-accumulating) mutants of Phycomyces blakesleeanus have been characterized with respect to their carotene contents, in vitro formation of isoprenoids from [2-¹⁴C] mevalonic acid and their ability to produce [¹⁴C]phytoene in situ for use in coupled assays of phytoene desaturase activity. All strains produced predominantly (15-Z)-phytoene both in vivo and in vitro. Other isoprenoids were produced by cell extracts including squalene, sterols, prenyl diphosphates and prenyl alcohols. The addition of 1% Tween 60 to crude cell extracts of the mutants partially restored wild type carotenogenic activity and also altered the proportions of other isoprenoids formed. However, in a cytosolic fraction of the car B mutant, the addition of 1% Tween 60 did not result in the production of any carotenoid from phytoene. This fraction was the most effective source of [¹⁴C] phytoene for use in coupled assays of phytoene desaturase activity.     

四川裂腹鱼耳石碳、氧稳定同位素特征

为探讨耳石碳(δ¹³C)、氧(δ¹⁸O)稳定同位素在淡水鱼类群体识别中的作用,本研究以养殖条件下不同年龄组四川裂腹鱼为对象,采用稳定同位素质谱仪进行碳、氧同位素测定,揭示耳石中碳、氧稳定同位素特征,探讨其与环境间的关系. 结果表明:1⁺龄四川裂腹鱼δ¹³C和δ¹⁸O值均与耳石质量无显著相关关系,但在微耳石和星耳石之间存在显著差异;不同年龄四川裂腹鱼微耳石δ¹³C和δ¹⁸O平均值分别为(-9.58±0.06)‰、(-8.33±0.17)‰,其在雌雄个体之间均无显著性差异,但在不同年龄组间存在显著差异. 耳石δ¹⁸O和δ¹³C的关联分析能有效区分四川裂腹鱼不同养殖年龄群体,可作为一种识别淡水鱼类养殖群体的手段.     

长白山红松年轮碳同位素与净初级生产力的关系

解析树木年轮碳同位素变化是揭示气候与环境变化的有效途径,然而少有研究分析年轮碳同位素对森林净初级生产力(NPP)的指示效应.基于生长季气象因子,分析了长白山红松年轮δ¹³C记录序列与阔叶红松林红松种群NPP变化趋势以及两者之间的相关关系.结果表明: 1970年以前,研究区红松年轮δ¹³C与红松种群NPP变化同步,且两者间呈极显著线性正相关关系,年轮δ¹³C记录了气候变化对红松种群NPP的影响;1970年以后,红松年轮δ¹³C与红松种群NPP变化出现分异,两者呈负相关关系但相关性不显著,表明干旱等其他环境因子的影响使年轮δ¹³C对气候变化的敏感性和对NPP指示性降低.这一相关关系在红松年轮δ¹³C与当年和下一年红松种群NPP之间都存在,表明当年环境状况对来年红松生长的重要意义.说明长白山红松年轮δ¹³C对红松种群NPP有良好的指示性,树木年轮δ¹³C有重建森林历史NPP长期变化的潜力.